Rhizosphere effects of maize hybrids and N forms on Cd bioavailability in a limed soil

Abstract

Replacing new corn genotypes in agricultural practices requires adequate information on the reaction of the selected hybrids to Cd uptake in Cd-polluted soil and an understanding of interactions with N fertilizers. A 2 × 2 × 3 factorial pot experiment with limed soil (pH 8), two maize (Zea mays) hybrids (Pioneer cultivar yellow and Pioneer cultivar white), two N fertilization forms (NH₄ ⁺ and NO₃ ⁻) and three Cd exposures (0, 2 and 5 mg kg⁻¹ soil) was conducted under greenhouse conditions. Shoot dry mass increased significantly with NH₄ ⁺ nutrition compared with NO₃ ⁻ nutrition in both maize hybrids, with greater negative influence of Cd application combined with NH₄ ⁺ nutrition. The yellow cultivar had significantly greater shoot dry mass and lower Cd uptake than the white cultivar. Both hybrids exhibited similar N uptake in shoots and roots, with the exception of yellow cultivar with NH₄ ⁺ nutrition without Cd application. NO₃ ⁻ nutrition always decreased Cd uptake in both cultivars compared with NH₄ ⁺ nutrition. The N balance (mean across cultivars and Cd supply) after harvest showed most N uptake with NH₄ ⁺ nutrition (63.4%) and N_min remains in the soil with NO₃ ⁻ nutrition (48.7%). Soil pH decreased more with NH₄ ⁺ (−0.95 pH units) than NO₃ ⁻ nutrition (−0.21).

Keywords:

• maize hybrids
• N form
• N uptake
• Cd uptake
• N balance